There are various prior-art methods for coupling pipes which at their end have a circumferential bead. The applicant's PCT Publication WO 96/07848 discloses how a so-called clamping band is tightened around circumferential end beads of two pipes which are arranged end to end. This known clamping band is annular and its cross-section is in the shape of a U, the flanges of which are directed towards the pipes and are arranged on each side of the end beads and the web of which is placed radially outside the end beads. In the coupling operation, the clamping band is tightened around the end beads by means of a clamping mechanism, and in a preferred embodiment there is a seal between the inside of the clamping band and the outside of the end beads.
Practical designs of the above-described clamping band, which are available on the market, are shown in the applicant's catalogue "Ventilation 96" from 1996, p. 6/42, and in an advertisement placed in the magazine "Platslageri" (in English: Plate Works), No. 11/96.
These prior-art clamping bands function in a satisfactory manner in terms of construction, but certain drawbacks arise during mounting. The fitter must in fact hold the end beads of the two pipes joined at the same time as the clamping band is applied and tightened. Since piping systems, e.g. ventilation ducts, where the clamping band is used are often placed in a position high above the floor, the fitter usually stands on a ladder and handles the clamping band in the original mounting of the pipes or in later dismounting thereof for cleaning purposes. Holding the two pipes with one hand and tightening the clamping band with the other hand is a complicated operation for the fitter, especially if the fitter is placed in an uncomfortable working position. In a worst case, for instance in connection with large pipe dimensions, two fitters may be required to couple together pipes by means of clamping bands of the above-mentioned type.
A further drawback of these prior-art clamping bands is that sometimes sealing problems arise in the joint between the two clamping band ends where the clamping mechanism is arranged. This problem is stressed especially by the fact that the seal placed on the inside of the clamping band usually is slotted and has Its opposite ends in the area of the joint between the opposite ends of the clamping band.
There is thus a need of a more rational method and an improved device for coupling together pipes of the above-mentioned type, while at the same time a perfect sealing function is ensured.
As a further example of prior-art technique, mention can be made of the device according to EP-A-287,755 (counterpart; U.S. Pat. No. 4,882,083) for coupling together two pipes having end flanges. This device comprises a clamping band which is applied around the end flanges of the pipes placed end to end, but the fitter using this clamping band experiences the same difficulties as discussed above. The clamping band according to the European publication thus offers no solution to the inconveniences described above.